There has been a trend in the semiconductor industry in increasing the packaging density of wafers. The high integration level of semiconductor ICs has been achieved by reducing the device dimension. Similar to other aspects of integrated circuit processing, the technology for fabricating contacts has to evolve in order to keep up with the pace of other advancements in the process sequence.
A contact in a semiconductor integrated circuit allows electrical connection between metal conductors and circuit elements in the semiconductor integrated circuit substrate. In a common application for integrated circuit fabrication, a dielectric layer is formed on a semiconductor substrate. A contact opening is etched through the dielectric layer to the semiconductor substrate. The contact opening is then filled with a conductive material (e.g., titanium) to provide an electrical connection between the metal conductors and the circuit elements. In order to prevent chemical reactions between the metal conductor and the substrate or between the metal conductors, a barrier layer used as a barrier, such as a titanium nitride layer, is deposited over the conductive layer.
A well known process for depositing metal films is chemical vapor deposition (CVD). A commonly used method of forming a contact involves the application of a chemical vapor deposition titanium (Ti) process followed by a chemical vapor deposition titanium nitride (TiN) process. The CVD Ti deposition process is conducted at a high temperature, for example between about 500° C. and 650° C., so that titanium silicide (TiSi2) forms immediately when Ti layer is deposited. FIGS. 1A and 1B illustrate a method for manufacturing a contact. As shown in FIG. 1A, a semiconductor substrate 102 with a dielectric layer 104 and an opening 106 are provided. A titanium layer 110 is then deposited by plasma enhanced chemical vapor deposition (PECVD) as shown in FIG. 1B. Further, a titanium nitride barrier layer 114 is deposited prior to deposition of certain metal conductors 116 such as aluminum or tungsten. Titanium nitride layer 114 is deposited by a chemical vapor deposition process. A titanium silicide region 112 is formed due to the reaction of titanium with silicon.